This invention relates to an optical pickup for recording/reproducing data in/from an optical recording medium such as an optical disc, a damper base for use in the optical pickup, and an adjustment method for adjusting the damper base.
In the manner known in the art, an electric equipment such as a personal computer is connected to various peripheral units one of which comprises a memory device or a recording medium. In addition, there is various types of memory devices (recording media). In other words, the memory devices (recording media) are classified into removable media and non-removable media. On of the removable media comprises a compact disc-recordable (CD-R). The compact disc-recordable is an audible recording medium which is compatible with a compact disc read only memory (CD-ROM) or a compact disc-digital audio (CD-DA). Although to write information (data) in the CD-R requires an exclusive apparatus or a CD-R drive and a writing application, to read the information (data) from the CD-R may be carried out by using a CD-ROM drive. Although it is impossible to cancel the date once written, it is possible to frequently add data.
Various other removable media are already known. A compact disc-rewritable (CD-RW) is a compact disc which is capable of erasing data therefrom and of rewriting data therein many times.
Now, in order to write information (data) in the CD-R or the CD-RW and to read the information (data) from the CD-R or the CD-RW demands a recording/reproducing optical pickup requires for irradiating a laser beam on the CD-R or the CD-RW.
In general, the optical pickup of the type described comprises a laser optical source for outputting the laser beam and an optical system for guiding the outputted laser beam to a recording medium such as an optical disc. As described above, it is possible for the CD-R and the CD-RW to carry out not only reading of information but also writing of information. In the optical pickup for the CD-R and the CD-RW, it is necessary to change output or power of the laser beam outputted by the laser optical source either on reading of information or on writing of information. This is because writing of information is carried out by forming a pit in a recording layer of the optical disc by irradiating of the laser beam. Accordingly, the output of the laser beam on writing of information is larger than that on reading of information and is, for example, ten to twenty times as large as that on reading of information.
The optical pickup comprises an object lens, a lens holder for holding the object lens, a damper base for shiftably supporting up and down and right and left the lens holder through a plurality of suspension wires, and actuator base including a supporting block for fixedly supporting the damper base by using a screw.
In the manner which will later be described in conjunction with FIG. 5, a conventional damper base has a circular hole which merely allows the screw to pass therethrough. With this structure, it is possible to correct an angular displacement of the object lens in a radial direction in regard to an optical axis by fastening the damper base to the supporting block with the damper base suitably rotated about the screw.
The above-mentioned damper base merely can adjust an angle of the object lens in the radial direction in regard to the optical axis. However, it is actually necessary not only to correct the angular displacement of the object lens in the radial direction that occurs on assembling and so on but also to correct a position displacement of the object lens in the radial direction. This assemble requires a precision of about tens of microns.